Relationship between leaf structure and carbon isotope discrimination in field grown barley

Jordi Bort, José Luis Araus, Salvatore Ceccarelli, Stefania Grando, Hani Hazzam. (30/4/1999). Relationship between leaf structure and carbon isotope discrimination in field grown barley. Plant Physiology and Biochemistry, 36 (12), pp. 889-897.

Abstract

For C-3 plants, discrimination against C-13 (Delta) is an integrated indicator of the ratio of intercellular to atmospheric partial pressure of CO2 (p(i)/p(a)) and therefore of the water use efficiency (WUE). Changes in p(i)/p(a), and thus in Delta, can arise from changes in the balance between leaf stomatal conductance and photosynthetic capacity. If the intrinsic photosynthetic capacity of leaves is increased, p(i)/p(a) and Delta could decrease and WUE could be improved, without compromising potential yield. A set of F-6 lines of two-row barley derived from two parents, Tadmor and WI 2291, with contrasting leaf chlorophyll content, was cultivated in Tel Hadya (the headquarters of ICARDA), in North-west Syria. without apparent drought stress. Here, we examine the relationship between Delta and different leaf structural indicators of photosynthetic capacity in barley (Hordeum vulgare L.). Total chlorophyll content (SPAD) was measured in penultimate leaf blades, around 2 weeks before anthesis, with a portable meter in the field. Further, the specific leaf dry weight (SLDW) and the nitrogen content and carbon isotope discrimination (Delta) was measured in the same leaves. The SLDW was positively correlated with both nitrogen (SLNW) and chlorophyll (SPAD) content per unit leaf area, which in turn were negatively correlated with Delta of leaf dry matter (Delta-DW). The Delta of the water soluble fraction (Delta-SF) from the same leaves was further analyzed to provide information on the discrimination of the current photoassimilates, therefore ignoring the photoassimilates coming from other parts of the plant during leaf development. Correlation between Delta-SF and either SLDW or SLNW was consistently higher than correlations with Delta-DW. The leaf parameter best correlated with Delta, of either total dry matter or the soluble fraction, was SLDW, indicating that genotypes with thicker and/or more compact leaves have lower Delta. The results suggest that SLDW and SPAD measurements can be used as a single, rapid surrogate for Delta in barley.